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Wiring diagrams Section: Automatic Trans

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Automatic Transmission 4AT (Diagnostics): Wiring Subaru Forester SH

Automatic Trans

WIRING DIAGRAM

Step	Check	Yes	No
1 CHECK HARNESS CONNECTOR BETWEEN TCM AND ATF TEMPERATURE SENSOR . Turn the ignition switch to OFF. Disconnect the connector from TCM. Measure the resistance between TCM connector terminals. Connector & terminal (B55) No. 23 - No. 12	Is the resistance 500 ohms or more?	Go to step 2 .	Go to step 4 .
2 CHECK HARNESS CONNECTOR BETWEEN TCM AND ATF TEMPERATURE SENSOR . Measure the resistance of the harness between TCM connector and chassis ground. Connector & terminal (B55) No. 23 - Chassis ground	Is the resistance 1 Mohms or more?	Go to step 3 .	Go to step 4 .
3 CHECK HARNESS . Measure the resistance between TCM connector terminals while shaking the harness. Connector & terminal (B55) No. 23 - No. 12	Does the resistance change?	Go to step 4 .	Replace the TCM. Refer to TRANSMISSION CONTROL MODULE (TCM) .
4 CHECK HARNESS CONNECTOR BETWEEN TCM AND ATF TEMPERATURE SENSOR . Turn the ignition switch to OFF. Disconnect the connector from transmission. Measure the resistance of the harness between TCM connector and chassis ground. Connector & terminal (B55) No. 23 - Chassis ground	Is the resistance 1 Mohms or more?	Go to step 5 .	Repair the short circuit of harness between TCM and transmission harness.
5 CHECK HARNESS CONNECTOR BETWEEN TCM AND ATF TEMPERATURE SENSOR . Measure the resistance of the harness between TCM connector and chassis ground. Connector & terminal (B55) No. 12 - Chassis ground	Is the resistance 1 Mohms or more?	Go to step 6 .	Repair the short circuit of harness between TCM and transmission harness.
6 CHECK ATF TEMPERATURE SENSOR . Measure the resistance between transmission connector terminals. Connector & terminal (T4) No. 11 - No. 15	Is the resistance 500 ohms or more?	Check for short circuits in the harness or connectors, and repair the fault location.	Go to step 7 .
7 CHECK TRANSMISSION HARNESS . Lift up the vehicle. Drain the automatic transmission fluid. CAUTION: Do not drain ATF until it cools down. Remove the oil pan. Disconnect the harness connector from control valve. Measure the resistance between transmission connector and transmission ground. Connector & terminal (T4) No. 11 - Transmission ground	Is the resistance 1 Mohms or more?	Go to step 8 .	Replace the transmission harness.
8 CHECK TRANSMISSION HARNESS . Measure the resistance between transmission connector and transmission ground. Connector & terminal (T4) No. 15 - Transmission ground	Is the resistance 1 Mohms or more?	Go to step 9 .	Replace the transmission harness.
9 CHECK ATF TEMPERATURE SENSOR . Measure the resistance between control valve connector terminals. Connector & terminal (AT2) No. 4 - No. 9	Is the resistance 500 ohms or more?	Check for short circuits in the harness or connectors, and repair the fault location.	Replace the control valve body. Refer to CONTROL VALVE BODY .

CAUTION
Do not drain ATF until it cools down.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK DTC .	Is DTC of CAN communication displayed?	Perform diagnosis according to the DTC.	Go to step 2 .
2 CHECK BODY INTEGRATED UNIT . Turn the ignition switch to OFF. Connect the Subaru Select Monitor to the data link connector. Turn the ignition switch to ON. Run the Subaru Select Monitor. Read the data of "Stop Light Switch" using the Subaru Select Monitor. Refer to OPERATION , Subaru Select Monitor.	Is OFF displayed?	Go to step 3 .	Go to step 4 .
3 CHECK TCM . Read the data of "Stop Light Switch" using the Subaru Select Monitor. Refer to OPERATION , Subaru Select Monitor.	Is OFF displayed?	Check for poor contact in the connector or harness, and repair the fault location.	Replace the TCM. Refer to TRANSMISSION CONTROL MODULE (TCM) .
4 CHECK BODY INTEGRATED UNIT INPUT SIGNAL . Disconnect the harness connector of body integrated unit. Measure the voltage of harness between body integrated unit and stop light switch. Connector & terminal (B280) No. 2 (+) - Chassis ground (-)	Is the voltage 10 V or more?	Go to step 5 .	Go to step 7 .
5 CHECK STOP LIGHT SWITCH . Turn the ignition switch to OFF. Disconnect the connector from stop light switch. Measure the resistance of harness between stop light switch connectors. Connector & terminal (B65) No. 2 - No. 3	Is the resistance 1 Mohms or more?	Go to step 6 .	Replace the stop light switch.
6 CHECK HARNESS CONNECTOR BETWEEN BODY INTEGRATED UNIT AND STOP LIGHT SWITCH . Turn the ignition switch to ON. Measure the voltage of harness between the body integrated unit and chassis ground. Connector & terminal (B280) No. 2 (+) - Chassis ground (-)	Is the voltage less than 1 V?	Go to step 7 .	Repair the short circuit of harness between TCM and stop light switch.
7 CHECK POOR CONTACT .	Is there poor contact in input signal of brake switch?	Repair the poor contact.	Check the body integrated unit.

DIAGNOSTIC PROCEDURE